The present invention relates to determining cycle information with medical diagnostic ultrasound data. In particular, cyclic events are identified with ultrasound data and without an ECG input.
Knowledge of the end-diastolic (ED) and end-systolic (ES) image frame locations in a cardiac cycle allows for quantitative evaluation of the left-ventricular (LV) function using measures such as ejection fraction (EF), stroke volume (SV), or cardiac output (CO). These measures depend on the volumes enclosed by the LV walls at ED and ES time. At the ED time, the LV has the largest enclosed volume, and, at ES time, the LV has the smallest enclosed volume.
Traditionally, identification of these two frames in a cardiac cycle is carried out manually. A user scrolls through or plays a sequence of 2D image frames of a cardiac cycle in a loop and marks the image frame corresponding to the largest area of the LV cross-section as the ED frame and that with the smallest area of the LV cross-section as the ES frame. Given an ECG signal, the ED frame may be identified as the frame that falls immediately after the R-wave peak, but the ES frame is detected manually. Manual identification can be subjective and time consuming. Manual identification also typically occurs after an image sequence is obtained and saved, limiting the ability to alter the acquisition of data based on identification of cycle timing information. Occasionally, an ECG sensor or input signal is not available to reduce the amount of manual identification.
A formula may be used to compute the ES time or duration of the LV ejection fraction (LVEF). The formulas may replace the manual searching of the ES image frame. In milliseconds and given the heart rate (HR) and gender, the formulas are:Male: HR×(−1.7)+413,   (1)Female: HR×(−1.6)+418,   (2)where HR is the heart rate. The approximate location of the ES frame of data is determined by looking at the timestamps on the image frames. These formulas give good results with heart rates up to about 120 to 150 beats per minute (bpm). For higher heart rates, the formulas tend to produce intervals that are too short.